Hybrid approach for performance enhancing proxies

ABSTRACT

There are provided a transparent performance enhancing proxy, a method for operating a transparent performance enhancing proxy between a source device and a destination device, and corresponding computer program product. The method includes preserving, without translation, packet header information of a header for a packet received from the source device to be forwarded to the destination device. The method further includes during a transmission control protocol connection setup phase for the packet, preserving transmission control protocol connection semantics. The method also includes during a transmission control protocol data transfer phase for the packet, running a transmission control protocol by masquerading as the source device to the destination device and masquerading as the destination device to the source device to transmit the packet to the destination device with the preserved packet header information.

BACKGROUND

1. Technical Field

The present invention relates generally to information processing and,in particular, to a hybrid approach for performance enhancing proxies.

2. Description of the Related Art

A fundamental problem in using Transmission Control Protocol/InternetProtocol (TCP/IP) over wireless networks is TCP's default behavior ininterpreting packet losses as a sign of network congestion. While thisassumption is useful in wired networks, where packet losses are mainlycaused by buffering limits in routers, it causes problems in wirelessnetworks. This is because in wireless networks, packet losses can occurdue to issues such as fading, attenuation, and collisions, problemsunique to using the air as the transmission channel. These packet lossescan unnecessarily restrict performance, leaving the wireless channelunder-utilized.

There have thus been approaches to mitigate this problem by decouplingpacket loss from congestion control, through the following twoapproaches:

-   (a) modifying the end-host TCP protocol stack; or-   (b) inserting a middlebox, known as a performance-enhancing proxy,    close to the wireless link.

The first approach is difficult to deploy since it relies on upgradingall the clients and all the servers that utilize the wireless link,typically an extremely difficult process due to the wide variety ofmobile devices and server operating systems.

The second approach is easier to deploy, since it can be doneincrementally, as well as transparently to the client and server.However, the second approach, as implemented in the prior art, suffersfrom many deficiencies including, but not limited to, changing thesemantics of the TCP connection in undesirable manners that can causeincorrect behavior by the sender.

SUMMARY

According to an aspect of the present principles, there is provided amethod for operating a transparent performance enhancing proxy between asource device and a destination device. The method includes preserving,without translation, packet header information of a header for a packetreceived from the source device to be forwarded to the destinationdevice. The method further includes during a transmission controlprotocol connection setup phase for the packet, preserving transmissioncontrol protocol connection semantics. The method also includes during atransmission control protocol data transfer phase for the packet,running a transmission control protocol by masquerading as the sourcedevice to the destination device and masquerading as the destinationdevice to the source device to transmit the packet to the destinationdevice with the preserved packet header information.

According to another aspect of the present principles, there is provideda computer program product for operating a transparent performanceenhancing proxy. The computer program product includes a computerreadable storage medium having program instructions embodied therewith.The program instructions are executable by a processor included in thetransparent performance enhancing proxy to cause the transparentperformance enhancing proxy to preserve, without translation, packetheader information of a header for a packet received from the sourcedevice to be forwarded to the destination device. Moreover, the programinstructions executable by the processor included in the transparentperformance enhancing proxy cause the transparent performance enhancingproxy to, during a transmission control protocol connection setup phasefor the packet, preserve transmission control protocol connectionsemantics. Further, the program instructions executable by the processorincluded in the transparent performance enhancing proxy cause thetransparent performance enhancing proxy to, during a transmissioncontrol protocol data transfer phase for the packet, running atransmission control protocol by masquerading as the source device tothe destination device and masquerading as the destination device to thesource device to transmit the packet to the destination device with thepreserved packet header information.

According to yet another aspect of the present principles, there isprovided a transparent performance enhancing proxy for disposing betweena source device and a destination device. The proxy includes a processorfor preserving, without translation, packet header information of aheader for a packet received from the source device to be forwarded tothe destination device. The proxy further includes a memory for storinga copy of the packet. During a transmission control protocol connectionsetup phase for the packet, the processor preserves transmission controlprotocol connection semantics. Moreover, during a transmission controlprotocol data transfer phase for the packet, the processor runs atransmission control protocol by masquerading as the source device tothe destination device and masquerading as the destination device to thesource device to transmit the packet to the destination device with thepreserved packet header information.

These and other features and advantages will become apparent from thefollowing detailed description of illustrative embodiments thereof,which is to be read in connection with the accompanying drawings.

BRIEF DESCRIPTION OF DRAWINGS

The disclosure will provide details in the following description ofpreferred embodiments with reference to the following figures wherein:

FIG. 1 shows an exemplary environment 100 to which the presentprinciples can be applied, in accordance with an embodiment of thepresent principles;

FIG. 2 shows another exemplary environment 200 to which the presentprinciples can be applied, in accordance with an embodiment of thepresent principles;

FIG. 3 further shows the transparent performance enhancing proxy (PEP)130 of FIG. 1 and the PEP 230 of FIG. 2, in accordance with anembodiment of the present principles;

FIG. 4 shows an exemplary method 400 performed by a transparentperformance enhancing proxy (PEP), in accordance with an embodiment ofthe present principles; and

FIG. 5 shows an exemplary hybrid (Split-Snoop) TCP handshake 500, inaccordance with an embodiment of the present principles.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The present principles are directed to a hybrid approach for performanceenhancing proxies. The performance enhancing proxies described hereinare intended to be located in between a sending device and a receivingdevice. As used herein, the term “in between” refers to any of anin-band configuration (FIG. 1) of a performance enhancing proxy (PEP)and a side-band configuration (FIG. 2) of a PEP.

We note that the following terms are used interchangeably herein:sending device; sender; source; and server. We further note that thefollowing terms are also used interchangeably herein: receiving device;receiver; destination; client device; and client. The interchangeabilityof such terms is readily appreciated by one of ordinary skill in theart.

FIG. 1 shows an exemplary environment 100 to which the presentprinciples can be applied, in accordance with an embodiment of thepresent principles. The environment 100 includes a server 110, a WideArea Network (WAN) 120, a performance enhancing proxy (PEP) 130, anaccess point 140, and a client device 150 (hereinafter “client” inshort). The PEP 130 is connected to the access point 140 over a LocalArea Network (LAN) 160.

In the environment 100, the PEP 130 is connected in an in-bandconfiguration. Accordingly, all traffic flows through the PEP 130.Hence, the PEP 130 is similar to a router in that the PEP 130 sees allpackets.

FIG. 2 shows another exemplary environment 200 to which the presentprinciples can be applied, in accordance with an embodiment of thepresent principles. The environment 200 includes a server 210, a WideArea Network (WAN) 220, a router 225, a performance enhancing proxy(PEP) 230, an access point 240, and a client device 250 (hereinafter“client” in short). The PEP 230 is connected to the access point 240over a Local Area Network (LAN) 260. Of course, the present principlesare not limited to the configuration shown in FIG. 2 or 3. For example,regarding FIG. 2, in another embodiment, the PEP 230 could be connectedto a Wide Area Network (WAN) in place of the LAN 260. In yet anotherembodiment, the PEP 230 can be incorporated within the access point 240.The preceding configurations described herein are merely illustrativeand, thus, one of ordinary skill in the art will consider these andother configurations in which PEP 230 (as well as PEP 330 describedbelow with respect to FIG. 3) can be used given the teachings of thepresent principles provided herein, while maintaining the spirit of thepresent principles.

In the environment 200, the PEP 230 is connected in a side-bandconfiguration. The router 225 redirects packets to the PEP 230. Theredirection by the router 225 can be performed, for example, but notlimited to, MAC-layer re-writing or tunneling. Accordingly, the PEP 230only sees the traffic redirected to it by the router 225.

FIG. 3 further shows the transparent performance enhancing proxy (PEP)130 of FIG. 1 and the PEP 230 of FIG. 2, in accordance with anembodiment of the present principles. The PEP 130/230 includes at leastone processor (CPU) 304 operatively coupled to other components via asystem bus 302. A cache 306, a Read Only Memory (ROM) 308, a RandomAccess Memory (RAM) 310, an input/output (I/O) adapter 320, two networkadapter 341 and 342, a user interface adapter 350, and a display adapter360, are operatively coupled to the system bus 302.

A first storage device 322 and a second storage device 324 areoperatively coupled to system bus 302 by the I/O adapter 320. Thestorage devices 322 and 324 can be any of a disk storage device (e.g., amagnetic or optical disk storage device), a solid state magnetic device,and so forth. The storage devices 322 and 324 can be the same type ofstorage device or different types of storage devices.

The network adapters 341 and 342 can be any of a wired network adapterand/or a wireless network adapter. That is, the network adapters 341 and342 can be of the same type (both wired or both wireless) or differenttypes. In an embodiment, the network adapter 341 is a wireless networkadapter and the network adapter 342 is a wired network adapter. Ofcourse, any number of network adapters can be used in accordance withthe teachings of the present principles, depending upon theimplementation.

A first user input device 352, a second user input device 354, and athird user input device 356 are operatively coupled to system bus 302 byuser interface adapter 350. The user input devices 352, 354, and 356 canbe any of a keyboard, a mouse, a keypad, an image capture device, amotion sensing device, a microphone, a device incorporating thefunctionality of at least two of the preceding devices, and so forth. Ofcourse, other types of input devices can also be used, while maintainingthe spirit of the present principles. The user input devices 352, 354,and 356 can be the same type of user input device or different types ofuser input devices. The user input devices 352, 354, and 356 are used toinput and output information to and from PEP 130/230.

A display device 362 is operatively coupled to system bus 302 by displayadapter 360.

In an embodiment, the PEP 130/230 can be a server. The PEP 130/230 canbe implemented as, for example, but is not limited to, a WANaccelerator, a web cache, and a network optimizer appliance/WIFIAccelerator (NOA/WAX).

Of course, the PEP 130/230 may also include other elements (not shown),as readily contemplated by one of skill in the art, as well as omitcertain elements. For example, various other input devices and/or outputdevices can be included in PEP 130/230, depending upon the particularimplementation of the same, as readily understood by one of ordinaryskill in the art. For example, various types of wireless and/or wiredinput and/or output devices can be used. Further, in some embodiments,user direct input devices can be omitted, with user inputs providedremotely through one or both of the network adapters 341 and 342.Moreover, additional processors, controllers, memories, and so forth, invarious configurations can also be utilized as readily appreciated byone of ordinary skill in the art. These and other variations of PEP130/230 are readily contemplated by one of ordinary skill in the artgiven the teachings of the present principles provided herein.

FIG. 4 shows an exemplary method 400 performed by a transparentperformance enhancing proxy (PEP), in accordance with an embodiment ofthe present principles. The transparent PEP can be, for example, PEP 130shown in FIG. 1 or the PEP 230 shown in FIG. 2. The transparent PEP islocated in between a sender and a receiver. The sender can be, forexample, the server 110 shown in FIG. 1 or the server 220 shown in FIG.2. The receiver can be, for example, the client 150 shown in FIG. 1 orthe client 250 shown in FIG. 2.

At step 410, responsive to a connection being established between thesender and the receiver, terminate the connection, and run the TCPprotocol as the sender to the receiver and the receiver to the sender,effectively creating two connections.

At step 420, preserve TCP options the receiver and sender havenegotiated such as path Maximum Transmission Unit (MTU), SACK, ExplicitCongestion Notification (ECN), and so forth.

At step 430, responsive to receiving a new data packet, copy the newdata packet, cache the copy of the new data packet, and forward the copyof the new data packet to the receiver.

At step 440, responsive to the identification of a packet loss for thecopy of the new data packet forwarded to the receiver, retransmit thecopy of the new data packet that has been cached. The identification ofthe packet loss can be made, for example, through duplicate ACKs,Selective Acknowledgement (SACK) blocks, retransmission timeout, and soforth.

At step 450, responsive to receiving an Acknowledgment (ACK) for thecopy of the new packet forwarded to the receiver, destroy the copy ofthe new data packet that has been cached.

Regarding step 430, the same is described as involving “destroying” acopy of a packet. The terms “destroying” or “destroy” encompass any of avariety of actions that has the effect of, for example, removing,cancelling, deleting, de-listing, or de-referencing a packet, or makingthe packet unusable or inaccessible. As examples, a packet may be“destroyed” by deallocating memory associated with the packet and givingthat memory back to an operating system, or by giving memory back to amemory pool.

A description will now be given regarding TCP sequence numbers, theSynchronize (SYN) flag, and acknowledgements (ACKs). TCP uses thesequence number to identify each byte of data. The sequence numberidentifies the order of the bytes sent from the source device and thedestination device so that the data can be reconstructed in the properintended order regardless of, e.g., reordering or packet loss duringtransmission. Also, the sequence number allows the destination device todiscard duplicate packets. The initial sequence number (ISN) exchangedbetween the source device and the destination device is arbitrary (e.g.,prevent sequence prediction attacks). If the SYN flag is set (1), thenthis is the initial sequence number of the actual first data byte, andthe acknowledged number in the corresponding ACK is then this sequencenumber plus 1. If the SYN flag is clear (0), then this is theaccumulated sequence number of the first data byte of this segment forthe current session. If the ACK flag is set (1), then the value of theACK field is the next sequence number that the receiver is expected,which serves to acknowledge receipt of all prior bytes if any. The firstACK sent by the source and the destination acknowledge the other'sinitial sequence number itself but not data.

A description will now be given regarding performance enhancing proxies.

Performance enhancing proxies (PEPs) come in many forms (link level, TCPlevel, Hypertext Transfer Protocol (HTTP) proxies), but a convenientapproach is at the TCP layer, since it benefits all TCP traffic (whichis the bulk of the traffic on the Internet).

TCP PEPs fall into two categories: Split-TCP; and Snoop-TCP. Bothimprove performance over wireless links, albeit in different ways, andhave different advantages and disadvantages.

In the case of Split-TCP, the PEP splits the connection from the sourceto the destination into two connections, either explicitly orimplicitly. In explicitly splitting the connection, Split-TCP usesdifferent IP addresses and TCP port numbers. In implicitly splitting theconnection, the PEP pretends to be the endpoint (destination) of aconnection from a source to the destination in each direction. That is,the PEP masquerades as the source to the destination and as thedestination to the source, using the same IP addresses. In either caseof Split-TCP, the source and destination do not need to be made aware ofthe use of the PEP(s) there between.

In the case of Snoop-TCP, the PEP controls the transmissions of the TCPsegments in both directions by, e.g., ACK filtering and reconstructionin the existing (non-split) connection. When duplicate TCP ACKs arereceived, with such condition being associated with a high likelihood ofa packet loss, the corresponding lost packet is retransmitted withoutthe source having any knowledge of the packet loss.

The present principles propose Split-Snoop, a hybrid approach toTCP-level performance-enhancing proxies. Split-Snoop is a novel andunobvious combination of features that arrive at a unique design pointwith the best of the advantages of the two approaches and a minimal setof disadvantages.

A description will now be given regarding Split TCP.

Split TCP terminates the TCP connection at the PEP, either explicitly(using different IP addresses and TCP port numbers), or implicitly (byusing the same IP addresses and masquerading as the server to the clientand as the client to the server).

Split TCP has the following advantages in that it improves performancein at least 4 ways:

-   (1) Split TCP allows quicker loss recovery over the wireless link;-   (2) Split TCP allows the congestion window of the sender to grow    more quickly due to lower roundtrip time;-   (3) Split TCP increases the size of the buffer space available to    the sender by advertising a larger receive window than the original    receiver; and-   (4) Split TCP allows improvements in protocol behavior over part of    the network by making available certain TCP functionality (e.g., by    enabling Selective Acknowledgement (SACK) over the wireless    components, or Large Windows over the wired link).

Split TCP has the following disadvantages:

-   (1) Split TCP changes the semantics of the TCP connection in two    important ways:-   (a) connection failure error codes are changed (e.g., by converting    what would be a no response error to a connection reset error),    which may cause incorrect behavior by the sender; and-   (b) data acknowledgements are returned to the sender by the PEP,    before being acknowledged by the client, leading the sender to    believe that the receiver has gotten the information when the    receiver has not, again potentially leading to incorrect sender    behavior;-   (2) Split TCP requires more processing and memory resources than    Snoop TCP;-   (3) Split TCP is relatively easy to detect since, to an outside    viewer, Split TCP modifies TCP packets (e.g., sequence numbers, TCP    options, packet checksums, and so forth).

A description will now be given regarding Snoop TCP.

Snoop TCP is an intelligent TCP-aware packet cache that monitors a TCPconversation, determines when a packet has been lost (before theoriginal sender does), and retransmits that packet on behalf of thesender.

Since Snoop TCP is closer to the receiver than the sender is, thisallows quicker loss recovery and thus better performance. Snoop TCP doesnot terminate TCP connections.

Snoop TCP has the following advantages:

-   (1) Snoop TCP allows quicker loss recovery over the wireless link;-   (2) Snoop TCP does not violate any TCP semantics;-   (3) Snoop TCP requires fewer resources (CPU and memory/state) than    Split TCP; and-   (4) Snoop TCP is harder to detect, since Snoop TCP causes fewer    changes to the TCP connection behavior.

Snoop TCP has the following disadvantages:

-   (1) connections will experience longer latencies with snoop as    compared to Split TCP; and-   (2) Snoop TCP shows lower performance gains compared to Split TCP.

Having described relevant aspects of Split TCP and Snoop TCP, a furtherdescription of Split-Snoop will now be given, in accordance with anembodiment of the present principles.

As noted above, the present principles propose Split-Snoop, a hybridapproach to TCP-level performance-enhancing proxies. Advantageously,Split-Snoop provides a unique design point with the best of theadvantages of the two approaches and a minimal set of disadvantages.

For example, but certainly not exhaustive, we mention the following.Similar to Snoop TCP, Split-Snoop caches packets and retransmits them onbehalf of the sender when necessary. Also similar to Snoop TCP,Split-Snoop preserves connection setup semantics, by not terminatingconnections until both sides have completed their connectionestablishment sequences. Additionally similar to Snoop TCP, Split-Snoopacknowledges data sent by the sender before the data has arrived at thereceiver.

Accordingly, in an embodiment, Split-Snoop can have the followingadvantages:

-   (1) Split-Snoop allows quicker loss recovery over the wireless link;-   (2) Split-Snoop allows the congestion window of the sender to grow    more quickly due to lower roundtrip times;-   (3) Split-Snoop preserves the connection-setup semantics of Snoop    TCP (e.g., Split-Snoop does not change the TCP connection failure    error codes, nor return data ACKS to the source by the PEP before    being acknowledged by the destination, nor terminate the connections    until both sides have completed their connection establishment    sequences), as Snoop TCP does, but Split TCP does not;-   (4) Split-Snoop requires fewer CPU and memory resources than Split    TCP;-   (5) Split-Snoop is harder to detect than Split TCP. Detecting    Split-Snoop requires understanding more complex dynamics;-   (6) Split-Snoop provides better interoperability (e.g.,    opportunities for effectiveness) over Split TCP. For example    Split-Snoop disturbs the packet sequence less than Split TCP.    Further, Split-Snoop is more robust to unexpected interactions than    Split TCP; and-   (7) Split-Snoop has equivalent or comparable performance to Split    TCP.

In an embodiment, Split-Snoop can have the following disadvantages:

-   (1) Split-Snoop violates the data transfer semantics of TCP, as    Split TCP does, but Snoop TCP does not. The sender TCP stack will    think data has been delivered to the client when the data may not    have been;-   (2) Split-snoop requires more CPU and memory resources than Snoop    TCP; and-   (3) Split-snoop is easier to detect than Snoop TCP.

FIG. 5 shows an exemplary hybrid (Split-Snoop) TCP handshake 500, inaccordance with an embodiment of the present principles.

At step 510, intercept, by the PEP 130/230, a sequence number X sent bythe source 110/210.

At step 520, forward, by the PEP 130/230, the sequence number X to thedestination 150/250.

At step 530, intercept, by the PEP 130/230, sequence number Y, ACK=X+1sent by the destination 150/250.

At step 540, forward, by the PEP 130/230, sequence number=y, ACK=X+1 tothe source 110/210.

At step 550, send, from the PEP 130/230, ACK=Y+1 to the destination150/250.

At step 560, intercept, by the PEP 130/230, ACK=Y+1 from the source110/210.

Split-Snoop thus provides a unique design point that achieves most ofthe performance benefits of Split TCP with most of the implementationand semantic benefits of Snoop TCP.

Thus, the hybrid approach embodied in Split-Snoop advantageouslyaggressively preserves all packet headers. Split-Snoop uses the sameheader information to avoid detection. Hence, no translation of headerinformation is necessary. In an embodiment involving transmissioncontrol protocol (TCP), the packet header information includes, forexample, but is not limited to, the following: at least one TCP portnumber (e.g., a source port number and/or a destination port number); aTCP sequence number; TCP header options (e.g., the information in one ormore of the Option-Kind field, the Option-Length field, and theOption-Date field); TCP Explicit Congestion Notification information;and so forth. In an embodiment involving Internet Protocol (IP), thepacket header options include, for example, but are not limited to, thefollowing: at least one IP address (e.g., a source address and/or adestination address); an IP hop count; an IP Time To Live (TTL); an IPType of Service (aka Differentiated Services Code Point (DSCP); IPExplicit Congestion Notification information, and so forth. In anembodiment involving media access control (MAC), the packet headeroptions include, for example, but are not limited to, the following: aMAC address, a virtual local area network tag, and so forth.

In an embodiment, the packet header information that is preservedwithout translation includes all information specified in all 10mandatory fields of the TCP header. In an embodiment, the packet headerinformation that is preserved without translation further includes allinformation specified in at least all mandatory options fields of theheader.

We note that TCP protocol operations and, hence, the operation of thePEP 130/230, can be described as involving a connection setup phase, adata transfer phase, and a connection termination phase. Connectionsbetween the source and the PEP and between the PEP and the destinationare established in the multi-step handshake method 500 shown in FIG. 5and pertaining to the connection setup phase that precedes entering thedata transfer phase. After the completion of data transmission duringthe data transfer phase, the connection termination phase closes theaforementioned connections and releases all allocated resourcestherefor.

The hybrid approach embodied in Split-Snoop behaves like Snoop TCP forthe connection setup phase (aka connection establishment phase). Hence,Split-Snoop preserves TCP connection semantics during the connectionsetup phase. Thus, for example, Split-Snoop waits for a SynchronizeAcknowledge (SYN-ACK) to return from the destination device and preventstermination of a connection between the source device and thedestination device until both the source device and the destinationdevice have completed their respective connection establishmentsequences (i.e., SYN, SYN-ACK, ACK, for full duplex communicationbetween the source device and the destination device).

Further, the hybrid approach embodied in Split-Snoop behaves like SplitTCP for the connection termination phase. Hence, Split-Snoop alsopreserves TCP connection semantics during the connection terminationphase. That is, after the completion of data transmission during thedata transfer phase, the connection termination phase closes theconnection between the source device and the proxy and the connectionbetween the proxy and the destination device, and releases all allocatedresources therefor.

Also, the hybrid approach embodied in Split-Snoop behaves like Split TCPfor the data transfer phase. Thus, Split-Snoop runs a transmissioncontrol protocol by masquerading as the source device to the destinationdevice and masquerading as the destination device to the source deviceduring the data transfer phase. As a result of such masquerading,Split-Snoop allows the congestion window of the sender to grow morequickly due to lower roundtrip time. That is, Split-Snoop increases agrowth rate of a congestion window size of the source device due tolower roundtrip times. The lower roundtrip time is due to the PEP beingcloser to the destination device than the source device. Thus, in anembodiment, Split-Snoop can achieve the same performance improvementsavailable for Split TCP.

The present invention may be a system, a method, and/or a computerprogram product. The computer program product may include a computerreadable storage medium (or media) having computer readable programinstructions thereon for causing a processor to carry out aspects of thepresent invention.

The computer readable storage medium can be a tangible device that canretain and store instructions for use by an instruction executiondevice. The computer readable storage medium may be, for example, but isnot limited to, an electronic storage device, a magnetic storage device,an optical storage device, an electromagnetic storage device, asemiconductor storage device, or any suitable combination of theforegoing. A non-exhaustive list of more specific examples of thecomputer readable storage medium includes the following: a portablecomputer diskette, a hard disk, a random access memory (RAM), aread-only memory (ROM), an erasable programmable read-only memory (EPROMor Flash memory), a static random access memory (SRAM), a portablecompact disc read-only memory (CD-ROM), a digital versatile disk (DVD),a memory stick, a floppy disk, a mechanically encoded device such aspunch-cards or raised structures in a groove having instructionsrecorded thereon, and any suitable combination of the foregoing. Acomputer readable storage medium, as used herein, is not to be construedas being transitory signals per se, such as radio waves or other freelypropagating electromagnetic waves, electromagnetic waves propagatingthrough a waveguide or other transmission media (e.g., light pulsespassing through a fiber-optic cable), or electrical signals transmittedthrough a wire.

Computer readable program instructions described herein can bedownloaded to respective computing/processing devices from a computerreadable storage medium or to an external computer or external storagedevice via a network, for example, the Internet, a local area network, awide area network and/or a wireless network. The network may comprisecopper transmission cables, optical transmission fibers, wirelesstransmission, routers, firewalls, switches, gateway computers and/oredge servers. A network adapter card or network interface in eachcomputing/processing device receives computer readable programinstructions from the network and forwards the computer readable programinstructions for storage in a computer readable storage medium withinthe respective computing/processing device.

Computer readable program instructions for carrying out operations ofthe present invention may be assembler instructions,instruction-set-architecture (ISA) instructions, machine instructions,machine dependent instructions, microcode, firmware instructions,state-setting data, or either source code or object code written in anycombination of one or more programming languages, including an objectoriented programming language such as Java, Smalltalk, C++ or the like,and conventional procedural programming languages, such as the “C”programming language or similar programming languages. The computerreadable program instructions may execute entirely on the user'scomputer, partly on the user's computer, as a stand-alone softwarepackage, partly on the user's computer and partly on a remote computeror entirely on the remote computer or server. In the latter scenario,the remote computer may be connected to the user's computer through anytype of network, including a local area network (LAN) or a wide areanetwork (WAN), or the connection may be made to an external computer(for example, through the Internet using an Internet Service Provider).In some embodiments, electronic circuitry including, for example,programmable logic circuitry, field-programmable gate arrays (FPGA), orprogrammable logic arrays (PLA) may execute the computer readableprogram instructions by utilizing state information of the computerreadable program instructions to personalize the electronic circuitry,in order to perform aspects of the present invention.

Aspects of the present invention are described herein with reference toflowchart illustrations and/or block diagrams of methods, apparatus(systems), and computer program products according to embodiments of theinvention. It will be understood that each block of the flowchartillustrations and/or block diagrams, and combinations of blocks in theflowchart illustrations and/or block diagrams, can be implemented bycomputer readable program instructions.

These computer readable program instructions may be provided to aprocessor of a general purpose computer, special purpose computer, orother programmable data processing apparatus to produce a machine, suchthat the instructions, which execute via the processor of the computeror other programmable data processing apparatus, create means forimplementing the functions/acts specified in the flowchart and/or blockdiagram block or blocks. These computer readable program instructionsmay also be stored in a computer readable storage medium that can directa computer, a programmable data processing apparatus, and/or otherdevices to function in a particular manner, such that the computerreadable storage medium having instructions stored therein comprises anarticle of manufacture including instructions which implement aspects ofthe function/act specified in the flowchart and/or block diagram blockor blocks.

The computer readable program instructions may also be loaded onto acomputer, other programmable data processing apparatus, or other deviceto cause a series of operational steps to be performed on the computer,other programmable apparatus or other device to produce a computerimplemented process, such that the instructions which execute on thecomputer, other programmable apparatus, or other device implement thefunctions/acts specified in the flowchart and/or block diagram block orblocks.

The flowchart and block diagrams in the FIGS. illustrate thearchitecture, functionality, and operation of possible implementationsof systems, methods, and computer program products according to variousembodiments of the present invention. In this regard, each block in theflowchart or block diagrams may represent a module, segment, or portionof instructions, which comprises one or more executable instructions forimplementing the specified logical function(s). In some alternativeimplementations, the functions noted in the block may occur out of theorder noted in the figures. For example, two blocks shown in successionmay, in fact, be executed substantially concurrently, or the blocks maysometimes be executed in the reverse order, depending upon thefunctionality involved. It will also be noted that each block of theblock diagrams and/or flowchart illustration, and combinations of blocksin the block diagrams and/or flowchart illustration, can be implementedby special purpose hardware-based systems that perform the specifiedfunctions or acts or carry out combinations of special purpose hardwareand computer instructions.

Reference in the specification to “one embodiment” or “an embodiment” ofthe present principles, as well as other variations thereof, means thata particular feature, structure, characteristic, and so forth describedin connection with the embodiment is included in at least one embodimentof the present principles. Thus, the appearances of the phrase “in oneembodiment” or “in an embodiment”, as well any other variations,appearing in various places throughout the specification are notnecessarily all referring to the same embodiment.

It is to be appreciated that the use of any of the following “/”,“and/or”, and “at least one of”, for example, in the cases of “A/B”, “Aand/or B” and “at least one of A and B”, is intended to encompass theselection of the first listed option (A) only, or the selection of thesecond listed option (B) only, or the selection of both options (A andB). As a further example, in the cases of “A, B, and/or C” and “at leastone of A, B, and C”, such phrasing is intended to encompass theselection of the first listed option (A) only, or the selection of thesecond listed option (B) only, or the selection of the third listedoption (C) only, or the selection of the first and the second listedoptions (A and B) only, or the selection of the first and third listedoptions (A and C) only, or the selection of the second and third listedoptions (B and C) only, or the selection of all three options (A and Band C). This may be extended, as readily apparent by one of ordinaryskill in this and related arts, for as many items listed.

Having described preferred embodiments of a system and method (which areintended to be illustrative and not limiting), it is noted thatmodifications and variations can be made by persons skilled in the artin light of the above teachings. It is therefore to be understood thatchanges may be made in the particular embodiments disclosed which arewithin the scope of the invention as outlined by the appended claims.Having thus described aspects of the invention, with the details andparticularity required by the patent laws, what is claimed and desiredprotected by Letters Patent is set forth in the appended claims.

What is claimed is:
 1. A method for operating a transparent performanceenhancing proxy between a source device and a destination device,comprising: preserving, without translation, packet header informationof a header for a packet received from the source device to be forwardedto the destination device; during a transmission control protocolconnection setup phase for the packet, preserving transmission controlprotocol connection semantics; upon establishment of a connectionbetween the source device and the destination device during thetransmission control protocol connection setup phase, locallyterminating the connection at the transparent performance enhancingproxy and creating a connection from the source device to thetransparent performance enhancing proxy and a connection from thetransparent performance enhancing proxy to the source device; and duringa transmission control protocol data transfer phase for the packet,running a transmission control protocol by masquerading as the sourcedevice to the destination device and masquerading as the destinationdevice to the source device to transmit the packet to the destinationdevice with the preserved packet header information.
 2. The method ofclaim 1, wherein the packet header information that is preserved withouttranslation comprises, at least one of: for transmission controlprotocol communication of the packet, at least one of a transmissioncontrol protocol port number, a transmission control protocol sequencenumber, and a transmission control protocol header option; for Internetprotocol communication of the packet, at least one of an InternetProtocol address, an Internet Protocol hop limit, an Internet ProtocolTime To Live, an Internet Protocol Type of Service, and an ExplicitCongestion Notification; and for media access control communication ofthe packet, at least one of a media access control address and a virtuallocal area network tag.
 3. The method of claim 1, wherein the packetheader information that is preserved without translation comprises allinformation specified in all mandatory fields of the header.
 4. Themethod of claim 3, wherein the packet header information that ispreserved without translation further comprises all informationspecified in at least some mandatory options fields of the header. 5.The method of claim 1, wherein the transmission control protocolconnection semantics are preserved for the connection setup phase bywaiting for a Synchronize Acknowledge to return from the destinationdevice and preventing termination of a connection between the sourcedevice and the destination device until both the source device and thedestination device have completed their respective connectionestablishment sequences for the connection.
 6. The method of claim 1,further comprising preserving transmission control protocol connectionsemantics for a connection termination phase for the packet by closing aconnection between the source device and the transparent performanceenhancing proxy, closing a connection between the transparentperformance enhancing proxy and the destination device, and releasingall allocated resources for the connections.
 7. The method of claim 1,further comprising: responsive to receiving the packet from the sourcedevice, creating a copy of the packet, caching the copy of the packet,and transmitting the copy of the packet to the destination device;responsive to receiving an acknowledgement for the packet from thesource device, destroying the copy of the packet that has been cached;and responsive to a detection of packet loss relating to the packet,retransmitting the copy of the packet that has been cached.
 8. Themethod of claim 1, further comprising preserving, for the connectionfrom the source device to the transparent performance enhancing proxyand the connection from the transparent performance enhancing proxy tothe source device, any transmission control protocol options previouslynegotiated between the source device and the destination device for theconnection there between.
 9. The method of claim 8, wherein thetransmission control protocol options comprise at least one of pathMaximum Transmission Unit, Selective Acknowledgement, and ExplicitCongestion Notification.
 10. A computer program product for operating atransparent performance enhancing proxy, the computer program productcomprising a non-transitory computer readable storage medium havingprogram instructions embodied therewith, the program instructionsexecutable by a processor comprised in the transparent performanceenhancing proxy to cause the transparent performance enhancing proxy to:preserve, without translation, packet header information of a header fora packet received from the source device to be forwarded to thedestination device; during a transmission control protocol connectionsetup phase for the packet, preserve transmission control protocolconnection semantics; upon establishment of a connection between thesource device and the destination device during the transmission controlprotocol connection setup phase, locally terminating the connection atthe transparent performance enhancing proxy and creating a connectionfrom the source device to the transparent performance enhancing proxyand a connection from the transparent performance enhancing proxy to thesource device; and during a transmission control protocol data transferphase for the packet, running a transmission control protocol bymasquerading as the source device to the destination device andmasquerading as the destination device to the source device to transmitthe packet to the destination device with the preserved packet headerinformation.
 11. The computer program product of claim 10, wherein thepacket header information that is preserved without translationcomprises, at least one of: for transmission control protocolcommunication of the packet, at least one of a transmission controlprotocol port number, a transmission control protocol sequence number,and a transmission control protocol header option; for Internet protocolcommunication of the packet, at least one of an Internet Protocoladdress, an Internet Protocol hop limit, an Internet Protocol Time ToLive, an Internet Protocol Type of Service, and an Explicit CongestionNotification; and for media access control communication of the packet,at least one of a media access control address and a virtual local areanetwork tag.
 12. The computer program product of claim 10, wherein thetransmission control protocol connection semantics are preserved for theconnection setup phase by waiting for a Synchronize Acknowledge toreturn from the destination device and preventing termination of aconnection between the source device and the destination device untilboth the source device and the destination device have completed theirrespective connection establishment sequences for the connection. 13.The computer program product of claim 10, further comprising preservingtransmission control protocol connection semantics for a connectiontermination phase for the packet by closing a connection between thesource device and the transparent performance enhancing proxy, closing aconnection between the transparent performance enhancing proxy and thedestination device, and releasing all allocated resources for theconnections.
 14. The computer program product of claim 10, furthercomprising preserving, for the connection from the source device to theproxy and the connection from the proxy to source device, anytransmission control protocol options previously negotiated between thesource device and the destination device for the connection therebetween.
 15. A transparent performance enhancing proxy for disposingbetween a source device and a destination device, the proxy comprising:a processor for preserving, without translation, packet headerinformation of a header for a packet received from the source device tobe forwarded to the destination device; and a memory for storing a copyof the packet, wherein during a transmission control protocol connectionsetup phase for the packet, the processor preserves transmission controlprotocol connection semantics, wherein the processor, upon establishmentof a connection between the source device and the destination deviceduring the transmission control protocol connection setup phase, locallyterminates the connection at the transparent performance enhancing proxyand creates a connection from the source device to the transparentperformance enhancing proxy and a connection from the transparentperformance enhancing proxy to source device, wherein during atransmission control protocol data transfer phase for the packet, theprocessor running a transmission control protocol by masquerading as thesource device to the destination device and masquerading as thedestination device to the source device to transmit the packet to thedestination device with the preserved packet header information.
 16. Thetransparent performance enhancing proxy of claim 15, wherein thetransmission control protocol connection semantics are preserved for theconnection setup phase by waiting for a Synchronize Acknowledge toreturn from the destination device and preventing termination of aconnection between the source device and the destination device untilboth the source device and the destination device have completed theirrespective connection establishment sequences for the connection therebetween.
 17. The transparent performance enhancing proxy of claim 15,wherein the processor preserves, for the connection between the sourcedevice and the transparent performance enhancing proxy and theconnection between the transparent performance enhancing proxy and thesource device, any transmission control protocol options previouslynegotiated between the source device and the destination device for theconnection there between.